NORCROSS - Extending a MARTA line into Gwinnett County could add nearly 10,000 new riders to the transit system and jump start redevelopment, a study by two community improvement districts said.

The study, released today, looked into extending the Metropolitan Atlanta Rapid Transit Authority's heavy rail line from the Doraville station through Norcross to Gwinnett Place Mall.

Gwinnett Village CID director Chuck Warbington said that at a cost of $250 million a mile, the 10.5-mile project is probably too expensive to fund. But the CID's next step will be to study light rail along a similar route, at a cost of just $50 million a mile.

Late last month, the region's Transit Planning Board recommended that light rail be extended to the mall. Light rail, like streetcars or trolleys, has less of a construction impact on communities and can transport fewer people than heavy rail, but with greater frequency.

"The ridership came out unbelievable," Warbington said of the projected numbers. "It shows the pent-up demand of transit users in Gwinnett."

The study was built on a rejected 1990 proposal that would have brought MARTA service to Gwinnett Place Mall. It added a fourth station to the original proposal and relocated others. According to the study, transit stations would be put near Amwiler Road and Buford Highway, on OFS property near Jimmy Carter Boulevard and Interstate 85, at the intersection of Indian Trail-Lilburn Road and Beaver Ruin Road and at the mall.

Transit-oriented developments could also be built at the stations, adding more riders and creating redevelopment opportunities in those areas.

Warbington said the project could help both quality of life and mobility on the region's congested roads.

"We're using it as an economic development tool," he said.

The study was conducted over the past year in partnership with MARTA and the Gwinnett Place CID. According to the study, the line would include both aerial and subway sections.

Nearly 21,000 people would board the line at those four new stations, according to projections, including an additional 9,843 MARTA riders.

Warbington said if the heavy rail plan went forward, it would take 20 to 30 years to build, while a light rail line could be completed in fewer than 10 years. Conducting this study, he said, will give planners a jumping-off point for future transit projects.

"The first question anybody asked was going to be, 'Why not just extend what MARTA has?'" Warbington said. "Now we know why."